This zone is exactly the same as the present (except there's no Konschtat Highlands yet so the zone is barricaded off). No surprise walls, so head to (G-10) and start hugging the left. This will take you off map to (G-11) where you'll hit the zone line for Grauberg (S).

To make your way back to the ???, just head to (F-5) (G/H-6 is a one way drop, so you need to go the longer way).